Split evaporator for cooling systems



1943- T. J. LEHANE ETAL 2,328,472

SPLIT EVAPORATOR FOR COOLING SYSTEMS Filed Jan. 19, 1942 111111111111111111111/1/ 1 1 I III] A mmm 2mg;

Patented Aug. 31, 1943 SYS TEMS

Timothy J. Lehane and Everett H. Burgess, Chicago, Ill.. assignors to Vapor Car Heating Company, Inc., Chicago, 111., a corporation of New York Application January 19, 1942, Serial No. 427,258

6 Claims.

This invention relates to certain new and useful improvements in a cooling or refrigerating system, and more particularly to an improved evaporator or heat absorber. may be known as a split evaporator, that is, it comprises a plurality of separately operating sections which may be used singly or simultaneously so as to vary the effective area of the evaporator. Also one or more-of the sections may be controlled by a cycling thermostat so as to cause the refrigerant to be supplied in successive separate impulses, these impulses increasing in number or duration as the temperature increases in the control space until, at amaximum temperature, the flow of refrigerant is continuous and the evaporator'section is utilized to its full capacity, In this way the effectiveness of the complete evaporator maybe varied between rather wide limits with a consequent flexibility and efliciency.

The principal object of this invention is, to provide an improved evaporator for a cooling system, as briefly described hereinabove and disclosed more in" detail in the specifications which follow.

Another object is to provide an improved split evaporator comprising a plurality of separately controlled sections.

Another object is to provide an improved thermostatic control system for the refrigerating apparatus.

Another object is to provide improved means for correcting the predetermined temperatures at which the different evaporator sections are successively effective.

Other objects and advantages of this invention are more apparent from the following detail description of one approved form of apparatus assembled and operating according to the princip es of this invention.

The accompanying drawing is a. partially diagrammatic and partial sectional view of the reirigerating system, and the electrical and thermostatic control mechanism cooperating-there'- with.

, The. improved evaporator A is housed in a conduit, shown partially at I, through which air is propelled in contact with the evaporator, as indicated by the arrow 2, although the direction of this air flow could be reversed. The evaporator comprises a pair of separate sections or coils indicated at A and A", these sections being arranged in parallel in the refrigerant circulation system. The smaller coil A may represent about of the capacity of the total cool- This evaporator er A, whereas the coil A has a maximum capacity of The evaporated refrigerant is drawn by suction through the pipe 3 into the compressor B driven by the motor C. The compressed refrigerant is discharged into the condenser D wherein it is cooled and flows in liquid form into the receiver E from which the liquid refrigerant flows out through pipe 4 to either or both of the magnetically actuated valves 5 and 6 which control the flow of refrigerant into the evaporator sections A" and A", respectively.

In the lower half of the figure is indicated digrammatically the electrical control mechanism. .The positive and negative electrical supply mains are indicated -at I and 8, respectively.

At 9 is shown a mercury-column thermostat which'is located was to respond to the temperature changes in the controlled space, that is it may. be positioned in the path of the air in conduit I after it has flowed-in contact with the evaporator A. This thermostat is so constructed that at some predetermined temperature, for example 72 F., the mercury column I!) which is constantly in contact with the lower fixed terminal II will engage an upper terminal l2 so as to complete an electric circuit vthrough the thermostat.

At 13 is shown a relay comprising the coil H which, when energized, will draw down the core l5 which,'through stem IE, will pull down the contact plate ll against the resistance of spring I8 until the spaced contacts l9 and 20' are bridged by plate ll. At the same time a second contact plate 2|, also on stem IE, will bridge a second pair of contacts 22 and 23.

When the predetermined temperature in the space, for example 72 F. is reached a current will flow from the positive main 1 through wire 24, resistor 25, thermostat 9, wire 25, relay coil [4 and wire 21 to the negative main 8. When the coil H is energized, the contact plates I! and 2| will be pulled down and a circuit will be completed from the positive main 1 through wire 28, relay contacts I9, I! and'20, wire 29, motor C, and wire 30 to the negative main. This will start operation of the motor C and conse quently of the compressor system. At the same time a circuit will be completed from wire 28 through relay contacts 22, 2| and 23, wire 3|, valve 5, and wire 32 to the negative main. This will open the valve 5 and hold it open so that there will be a flow of refrigerant through the smaller evaporator section A, as long as the temperature in the space controlled remains at or above 72 F.

If this 25% capacity evaporator is adequate to prevent further rise in the space temperature, the section A (and the compressor motor C) will remain continuously in service until the space temperature has been lowered below '12 whereupon the severalcircuits will be broken and valve 5 will close and the refrigerating sys- 7 space or subject to the same temperature as the first thermostat 9, is adapted to function at an atmospheric temperature of (for example 76.

However, the mercury in this thermostat is surrounded by or subject to the temperature of an auxiliary electric heating coil 34 which, when energized, will raise the temperature at the thermos'tat 2 so that the thermostat will actually function at an atmospheric temperature of 73 /2". (It will be understood that the temperatures here named are taken merely by way of example.) Now if the evaporator section A, operating at full capacity, is unable to prevent the rise of the space temperature above 72, when this space temperature reaches 73 /2 the mercury column 35 will contact the upper fixed contact 35.

At 31 is shown a relay (in many respects similar to th relay l3, already described) comprising a magnetic coil 38, a core 39, a retracting spring 40 adapted to lift the core when the coil is deenergized, a contact plate 4| adapted to engage.

the two fixed contacts 42 and 43 when the relay is energized, and a second contact plate 44 adapted to engage a second pair of contacts 45 and 46 when the relay is deenergized.

When relay-31 is deenergized, a current will ilow from the positive main 1 through wire 41, heating coil 34, wire 48, resistor 49, relay contacts 45, 44 and 46, and-wire 50 to the negative main 8. Consequently the heater 34 will be energized and will raise the temperature at thermostat 33 so that at an actual space temperature of 73 /2, this thermostat will close the following circuit: From th positive main through wire 5|, resistor 52, thermostat 33, wire 53, relay coil 38 and wire 54 to th negative main. The relay contacts will now be pulled down so that a circuit will be closed from .positive main 1 through wire 55, valve 6, wire 55, relay contacts 42, 4| and 43 and wire 50 to the negative main. As a result-the valve 5 will be opened and refrigerant will be permitted to flow from pipe 4 through valve. 5 to the larger evaporator coil A". However, th energizing circuit for auxiliary heater 34 will simultaneously be broken since the relay contact 44'will be pulled away from the contacts 45 and 45. Consequently the temperature affecting thermostat 33-will at once be lowered by'2 /2' (that is to approximately B whereas the effective temperature at this thermostat was formerly 76. The mercury column at this thermostat will, therefore, at once begin to lower and break'contact atthe terminal 35,

thus deenergizing the relay 3'! and permitting the valve 6 to close. Consequently only a momentary burst of refrigerant will be admitted to the evaporator section A, but the energizing circuit for heater 34 will immediately be closed again so that the effective temperature at thermostat 33 will again be raised to 76 or higher and the cycle of operations will again be repeated. This so called cycling thermostat will thus cause the valve 6 to be repeatedly opened and closed so as to intermittently admit refrigerant to the coil A". A" will only be partially eifective to increase the cooling operation and augment the section A which is still operating to its full capacity. If

the temperature in the space should continue to rise, the valve 5 will be held open for a greater portion of the time and the effectiveness of the section A" will be increased. If the temperature of the air flow should rise to 76, the thermostat 33 will remain continually closed and relay 3'! will be continuously energized so that valve 8 will remain open and the evaporator section A" will be utilized to its full capacity.

As the temperature in the controlled space is gradually lowered, the above cycle of operations will b reversed. The effective capacity of the section A" will be gradually cut down until thetemperature is lowered below B /2, whereupon the valve 6 will remain closed and section A" will be ineffective. When the space temperature is lowered below 72 the valve 5 will be closed and the section A will become ineffective. -At the same time the motor C will be stopped and the entire refrigerating system will be put out of service.

While the thermostat 9 has been described as functioning at an atmospheric temperature of 72, and the thermostat 33 at an atmospheric adjusted which flows as .follows: From positive main 1 through wire 41, heating coil 34, wires 48, 59 and 60 to and through rheostat contact 51, the selected portion of resistance 58, and wire 6| to the negative main. At the same time a similar shunt heating circuit is completed from the positive main through wire 62 to and through a heating coil 63 associated with the thermostat 9, and thence through wire 60 through rheostat R to the negative main. These heating currents are constantly flowing through each ofthe coils 63 and 34 and by suitably adjusting the rheostat R the functioning temperatures of the two thermostats 9 and 33 can be simultaneously adjusted without affecting the difference between these operating temperatures. It maybe noted that a portion ofthe "cycling current for heater 34 may also flow through the heater 63 on thermo-' stat 9, but this cycling current will only be made and broken at such times as the thermostat 9 is continuously closed so that the consequent variations in the temperature at this thermostat 9 will be of no consequence. We claim:

1. In a cooling system, means for supplying and circulating a refrigerant comprising a compressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a plurality of separate sections arranged in parallel in the refrigerant circuit, a pair of thermostatically controlled means responsive to temperature changes in the space cooled by the system, one of these means directing the continuous flow of refrigerant to one of the sections as long as the temperature is at or above a predetermined temperature and the other means also causing at least an intermittent flow of the As a result this 0011 refrigerant to a second section while the temperature is above another higher temperature, this flow to the second section becoming continuous at or above this predetermined maximum temperature.

2. In a cooling system, means for supplying and circulating a refrigerant comprising a compressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a plurality of separate sections arranged in parallel in the refrigerant circuit, a pair of thermostatically controlled mean responsive to temperature changes in the space cooled by the system, one of these meansstarting the refrigerant supply means and directing the continuous flow of refrigerant to one of the sections as long as the temperature is at or above a predetermined temperature, and the other means also causing at least an intermittent flow of the refrigerant to a second section while the temperature is at or above another higher temperature,

this flow to the second section. becoming continuous at or above a predetermined maximum temperature.

3. In a cooling system, means for supplying and circulating a refrigerant comprising a compressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a plurality of separate sections arranged in parallel in the refrigerant circuit, a pair of thermostatically controlled means responsive to temperature changes in the space cooled by the system, one .of these means directing the continuous flow of refrigerant to one or the sec-v tions as long as the temperature is at or above a I predetermined temperature and the other means also causing at least an intermittent flow of the refrigerant to a second section while the temperature is at or above another higher temperature, this flow to the second section becoming continuous at or above a predetermined maxi-- mum temperature, and means for simultaneously raising or lowering the predetermined temperatures by equal amounts.

4. In a cooling system, means for supplying and circulating a refrigerant comprising a compressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a pair of separate sections arranged in parallel in the refrigerant circuit, a valve for controlling the flow of refrigerant to each section, means comprising a thermostat functioning at a predetermined temperature to start the motor and open one valve to cause the continuous flow of refrigerant to one sectionso long as the temperature in the controlled space is at or above a predetermined temperature, means comprising J, second thermostat for intermittently opening and closing the other valve to provide at least a cycling fiow of refrigerant to the second section while the temperature in the space is at or above a second predetermined higher temperature, the flow to this second section becoming continuous at or above a predetermined maximum space temperature.

5. In a cooling system, means for supplying and circulating a refrigerant comprising a compressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a pair of separate sections arranged in parallel in the refrigerant circuit. a valve for controlling the'fiow of refrigerant to eachsection, means comprising a thermostat functioning at 'a predetermined temperature to start the motor and open one valve to cause the continuous flow of refrigerant to one section so long as the temperature in the controlled space is at or above a predetermined temperature, means comprising a second thermostat for intermittently opening and closing the other valve to provide at least a cycling flow of refrigerant to the second section while the temperature in the space is at 6. In a cooling system, means for supplying I and circulating a refrigerant comprising a com pressor interposed in the refrigerant circuit, a motor for driving the compressor, an evaporator comprising a pair of separate sections of different effective sizes, arranged in parallel in the refrigerant circuit, means comprising a valve at the inlet of the smaller section and a thermostat responsive to temperature. changes in the space cooled by the system for starting the motor and holding the valve open while the space temperature rises to or exceeds a predetermined temperature, means comprising a second valve at the inlet of the larger section, a second space-temperature responsive thermostat, and auxiliary heating means acting on said second thermostat for causing an intermittent flow of refrigerant to the larger section in accordance with the rise in the space temperature above a second predetermined higher temperature, the second section being used to full capacity when the temperature reaches a predetermined maximum.

TILIOTHY J. LEHANE. EVERETT H. BURGESS. 

